1. Field
Example embodiments of the inventive concepts relate to a boosting voltage generating technology. More particularly, example embodiments relate to a charge pump used in a semiconductor integrated circuit and a display driving system including the charge pump.
2. Description of Conventional Art
Many circuits requiring a high operational voltage may exist in a semiconductor integrated circuit. If circuits which are used with a device requiring a high operating voltage or which require a high operating voltage exist in a semiconductor integrated circuit, it may be necessary to generate a voltage higher than a power voltage in the integrated circuit. Charge pumps are boosting devices that use capacitors and perform based on the law of conversation of electric charge. Charge pumps that are configured to generate a voltage higher than a supplied power voltage are widely used in electronic devices, such as memories, flat panel displays, etc. Nonvolatile memories, such as electrically erasable programmable read only memories (EEPROMs) and flash memories, use a high voltage to read and write data, and flat panel displays use a high voltage to drive an organic light emitting diode (OLED) or a thin film transistor (TFT)-liquid crystal display (LCD).
In order for a charge pump to be applied to a mobile display driving circuit, a high driving current is needed. Since a higher voltage is also needed, the charge pump increasing a voltage from a lower supplied power voltage is needed. Also, since power is supplied from a portable battery, power efficiency is very important. In general, charge pumps receive a phase (or clock) signal that is an operation reference signal to boost a voltage using a capacitor. Then, the charge pumps send the boosted voltage to an output terminal through a switch. The output terminal may suffer from current consumption due to an external load connected to the output terminal. The output terminal may also suffer from current consumption because an output voltage is decreased from the boosted voltage if the current consumption is increased. Accordingly, charge pumps should be designed to constantly supply a boosted voltage despite current consumption.